The present invention relates to hole saws and, more particularly, to arbors for connecting them to drills.
Hole saws, affixed to portable hand-held drills, have broad application in the construction industry. Electricians and plumbers utilize them in building construction to prepare holes for passing large wires and pipes through building frames. They are also used for similar purposes in sheet metal aspects of the heating, ventilation and air conditioning industry.
A major factor in measuring competitive values of hole saws is the relative ease with which they can be affixed to common, portable, hand-held power drills. Hole-saw arbors have been developed to facilitate quick connection of hole saws to drills. Typically, an arbor is affixed by an integral drive shaft to a drill, and a hole saw is mated and secured to the arbor.
As shown in U.S. Pat. No. 4,036,560 to Clark et al., most current hole-saw arbors utilize a "quick disconnect" assembly, comprising a non-cylindrical drive shaft, a threaded receiving end of the shaft, and a drive collar slidably mounted on the shaft. The drive shaft is secured to a drill by conventional "chuck" means. A hole saw having a threaded, central securing hole, and two drive holes, is threaded onto the receiving end of the shaft, while the drive collar is in a retracted, or "mounting position". After the hole saw is "snugged up" to a shoulder adjacent the threads on the receiving end of the shaft, it is "backed off" to align drive pins, or "bosses", in the drive collar, with the drive holes in the saw. The drive collar then slides along the drive shaft to a "driving position", so that the drive bosses are inserted within the hole saw. The drive collar has an internal, axial aperture that matches the non-cylindrical shape of the drive shaft, so that axial rotation of the drive shaft also rotates the collar and affixed hole saw.
As the hole saw is utilized, occasionally a plug of material being cut lodges within the hole saw, or an operator wants to quickly switch to an alternative usage of the drill. The drive collar is then retracted to its mounting position, and the hole saw is unthreaded from the shaft. Any plug can then be easily pushed out of the hole saw, or the arbor can be removed, so that the drill is free for other purposes.
One major problem with this common type of "quick disconnect" hole-saw arbor system is that it limits efficiency of the hole saw and accuracy of resulting usage. By backing off the hole saw from firmly abutting the shoulder on the drive shaft, a certain amount of play is left between the shaft and hole saw. Consequently, the hole saw vibrates, or wobbles, during cutting. The resulting vibration decreases the accuracy of the cut, increases the amount of material being cut, and therefore the duration of hole saw use necessary to make the cut. Such increased wear and tear also decreases the useful life of the hole saw.
More recently, an improved "quick disconnect" hole-saw arbor has attempted to solve the "wobble" problem resulting from "backing off" the hole saw. The improved arbor calls for snugging up the hole saw against a shoulder on a threaded mounting shaft that is axially and rotatably adjustable within an encapsulating drive-boss housing or collar. The drive-boss housing includes an integral drive shaft at one end for attachment to a drill, and drive bosses at an opposed end, adapted to be inserted into corresponding drive holes in the hole saw. After the hole saw is "snugged up" to the shoulder on the mounting shaft, the shaft is rotated within the drive-boss housing to align the drive bosses with the drive holes in the hole saw. Then, the mounting shaft is moved axially within the housing from a mounting to a driving position, so that the drive bosses penetrate the drive holes. A spring-biased pivot arm on an exterior surface of the drive-boss housing moves a lock rod that secures the mounting shaft within either the mounting or driving position. Therefore, an operator's finger can depress the pivot arm to change positions.
Although such an improved "quick disconnect" pivot-arm arbor effectively solves the hole-saw "wobble" problem, the pivot-arm arbor has substantial deficiencies. During usage of a hole saw, saw dust and related fine particulate matter is invariably discharged into the air adjacent the arbor. The pivot-arm arbor includes moving parts that are unsealed, and exposed to such fine particles. Consequently, accumulation of the particles around the moving parts presents a substantial risk that the pivot arm, spring, or lock rod may become jammed, rendering the arbor unsafe or inoperable. Additionally, as the arbor spins during hole-saw use, centrifugal force will tend to push the lock rod and pivot arm out of engagement with the mounting shaft. This is especially a problem as the spring biasing the pivot arm necessarily ages and weakens. Finally, the complexity of the pivot-arm arbor mandates substantial manufacturing costs.
Consequently, because of inherent structural limitations, known hole-saw arbors are unable to afford safe, consistent, quick disconnection of hole saws from portable drills, while enabling an accurate cut and efficient use of the hole saw.
Accordingly, it is the general object of the present invention to provide an improved hole-saw arbor that overcomes the problems of the prior art.
It is another general object to provide an improved hole-saw arbor that affords safe, consistent, quick disconnection of the hole saw from an arbor affixing the saw to a drill.
It is yet another general object to provide an improved hole-saw arbor that facilitates quick disconnection of the hole saw from the arbor without utilization of additional tools.
It is a more specific object to provide a hole-saw arbor that eliminates vibration between a hole saw and an arbor affixed to the saw and drill.
It is another specific object to provide a hole-saw arbor that affords accurate cutting by the hole saw.
The above and other objects and advantages of this invention will become more readily apparent when the following description is read in conjunction with the accompanying drawings.